The present invention relates to a ceramic burner for use in an air heater of the type including adjacent conduits for a heating or fuel gas and combustion air, wherein the gas supply conduit includes a mixing and intake or mixing and aspiration region which is inclined with respect to the axis of the combustion chamber of the air heater, and wherein the air supply conduit is provided with air discharge nozzles which open into the mixing and aspiration region of the gas supply conduit.
Ceramic burners of this type are known for use in various types of air heaters, such as recuperators, regenerators or hot-blast stoves, and are particularly employed to produce the hot air necessary for blast furnaces. In this operation however, problems arise when the heating or fuel gas is used at a low pressure or with rapidly varying heating or calorific values. Due to the high throughput and associated high pressure drop, the gas pressure in many gas supply systems for older type blast furnace installations is so low that known burners of the above-mentioned type cannot ensure trouble-free combustion of the heating or fuel gas. Moreover, this low gas pressure is in most gas supply systems subject to large fluctuations, for example when one or more user devices are switched in or out. Such pulsating gas streams can be employed for combustion without the necessity of additional measures only in systems with a low backpressure, for example in boiler houses. Such pulsating gas streams cannot be used however for heating in air heaters having a high pressure loss in the brickwork.
Additional difficulties are presented when the heating or calorific value of the heating or fuel gas fluctuates sharply. In practice, this fluctuation can range between 3000 and 5000 kJ/m.sup.3. While at a low heating value a comparatively low amount of combustion air and about 30% more gas must be forced out, at a high heating value 1 Nm.sup.3 of gas is associated with approximately 1.3 Nm.sup.3 combustion air, with a higher nozzle outlet speed.